1. Field
Embodiments of the present invention relate to a decelerator configured so that the increase in axial thickness of a motor is restrained, and a deceleration ratio is effectively increased, and a motor brake with the same.
2. Description of the Related Art
In recent years, brakes used in vehicles have increasingly adopted a motor as a power source. A representative example of the brakes is a disc type motor brake adopting a motor as a power source of a driving device to press a frictional pad/
The disc type motor brake includes a disc rotated together with a wheel of a vehicle, a pair of frictional pads to press the disc, a carrier to support the frictional pads, a piston to push one of the frictional pads to the disc, a caliper housing supported at the carrier in an advance and retreat fashion, the caliper housing has a cylinder to receive the piston, a motor to generate rotational force in alternating directions, and a conversion unit to convert rotation of the motor into linear reciprocation and to transmit the linear reciprocation to the piston. A screw shaft coupled to the piston is generally used as the conversion unit.
In the motor brake with the above-stated construction, driving force from the motor is transmitted to the screw shaft constituting the conversion unit, and the piston is linearly reciprocated in the rotation direction of the screw shaft in a state in which rotation of the piston is restricted to push the frictional pads to the disc, thereby performing a braking operation.
Generally, RPM of a motor is high, whereas torque of the motor is low. For this reason, a decelerator is generally used to increase the torque. In the motor brake, a decelerator to increase torque of the motor is connected between the motor and the conversion unit.
The decelerator generally includes a plurality of planet gear units stacked in the axial direction of the motor to increase a deceleration ratio, thereby achieving deceleration in multi stages.
However, the planet gear units stacked in the axial direction of the motor excessively increase the total length of the brake in the axial direction of the motor, thereby lowering space utilization of a vehicle.